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X-Ray Radiation from Supernova 1987A The Results of the Kvant Module in 1987-1989 R.A. SUNYAEV, A.S. KANIOVSKY, V.V. EFREMOV, S.A. GREBENEV, A.V. KUZNETSOV, E. CHURASOV, M. GILFANOV, N. YAMBURENKO1, J. ENGEHAUSER, S. DOEBEREINER, W. PIETSCH, C. REPPIN, J. TRUEMPER,2 E. KENDZIORRA, M. MAISACK, B. MONY, R. STAUBERT,3 G.K. SKINNER, T.G. PATTERSON, A.P. WILLMORE, O. AL EMAM,4 A.C. BRINKMAN, J. HETSE, J.J.M IN'T ZAND, R. JAGER5 ABSTRACT The results of two years SN1987A hard X-ray radiation observations by the HEXE instrument aboard the Kvant module are summarized. By May-June 1989, the hard X-ray flux had declined more than 8.5 tunes in comparison with the maximum of the X-ray light curve. The upper limit on the ratio of 57Co/56Co abundances at the level of ratio of 57Fe/56Fe abundances at the Earth by a factor of 1.5. INI8oDucrIoN The Roentgen international X-ray observatory on the Kvant module of the Mir space station has been operating successfully since the beginning of June 1987. Four telescopes mounted onboard the Kvant module cover a wide energy range: Coded Mask Imaging Spectrometer 1TM (2-30 keV), GSPC (2-100 keV); Phoswich type detectors HEXE (2~200 keV), and Phoswich type detectors Pulsar X-1 (50-1300 keV). Many of the X-ray sources were observed in 1987-1989, and appron- mate~ 30% of the observations were devoted to SN1987N 1 Space Research Institute, Academy of Sciences, Moscow 2Max-Planck-Institut fiir Extraterrestrische Physik Garching, FOG 3Astronomisches Institut der Univemitat ldbingen, FOG 4 Space Research Laboratory, Utrecht, The Netherlands a Department of Space Research, University of Birmingham, UK 368

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HIGH-ENERGY ASTROPHYSICS 369 For the first time during two years of observing Supernova 1987A in June 1989, the Roentgen observatory aboard the Mir-Kvant module was not able to detect its hard X-ray radiation dunog the current series of observations. The radiation flux in energy band 45-105 keV decreased more than 8.5 times in comparison with the mammal flux detected in January 1988. The results obtained during the two years of Supernova 1987A obser- vations were given in papers (Sunyaev et al. 1987a,b, 1988, 1989~. By the present time we have succeeded in calibrating the third and fourth detec- tors of the HEXE device using the results of the Crab Nebula observation. These detectors have a lower energr resolution in comparison with the first and the second ones. Therefore, we reprocessed all the obtained data about SN1987A hard X-rays using the results of all four detectors of the HEXE device, which increased data significance and decreased statistical errors. In Figure la,b, the spectra of SN1987A hard X-ray radiation are pre- sented. They were obtained in a series of seven intense observations earned out from the Roentgen observatory over two years. The spectra demon- strate an increase of the flux from August 1987 to January 1988. This increase is connected with a rapid decreasing of the envelope transparence. From January 1988 to June 1989 a continuous decline of the flux is ob- served which is mainly connected with a decreasing amount of 56CD in the envelope. Already in September 1988 a strong change of the spectral shape was detected. Ins is explained by a decreasing of the envelope optical thickness with respect to Thomson scattenng. The number of successive scattenngs experienced by the majority of photons became insufflcent to decrease the energy of the 56Co decay gamma-photons due to a multiple recoil effect up to a value of hv < 50 keV. Note that the sharp flux cutoff at the energies below 20 keV in August 1987 and January 1988 was connected with photoabsorption by heavy elements. At that time the photon diffusion in the envelope, accompanied by the recoil effect, moved the majority of photons in the band hv < 20 keV where the photoabsorption dominated. In Figure 2 and 3, the light curves of the SN1987A emission in three energy bands: 15~5, 45-105, 105-2130 keV (see also liable 1) are presented. Note here especially the pO=t corresponding to observations on June 16, 1987, when the hard X-ray 6= in the 45-105 keV spectral channel was detected at four standard deviation levels (it was first noticed by Englhauser et al. 1989~. The light curies (Figure 3) testified to a hard X-ray flux from the supernova, changed smoothly in accordance with predictions of the model of this radiation appearance due to radioactive cobalt decay in opaque envelope. For two years of observations we have not been able to observe

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370 2' AMERICAN AND SOVIET PElkSPECTIVES tes days(~) 9 - 320 days(33 o - 4 ~0 _5 ~0 LL ~. also days (2)4 .~ 20 . . . . ~. . . . lO ~So 2 20 3 40 ENERGY (ke V) O HEXE ~ Pulsar X-! o TTM 2 3 JO 40 o an> Q , . . . ~4 ~- 645 ~Y9~60 MU ~ o ~ 1 ~. , At; ~0 50-4 :~?'r.~ 1. ,& 1 ~ s . to S to 2 do ~ ENERGY (ke v) ~ ~1 2 ~0 ENERGY flue V) 1 -a own ~ FIGURE 1 The SN1987A X-ray spectra obtained by the Roentgen observatory in August 1987 (1) and October - November 1987 (2), December 1987 - January 1988 (3), April 1988 (4), September - October 1988 (5) and November 1988 (6), May - June 1989 (7), (diamonds and crosses - the HEXE and Pulsar X-1 data respectively, ausses marked By circles - the TIM telescope upper limits). The errors correspond to one standard deviation, the upper limits - to three standard deviations (in the last graph the HEXE upper limits are shown by tnangles). Results of the Monte-Carlo calculations carried out according to the envelope model accepted in the present paper are presented by solid lines (time after the outburst is shown near each cunre). In graphs 5,6,7 a 56 Co portion in the total 57Co emission is shown tar dotted lines. Ihe relative abundance of 56Co/57Co is equal to two-abundance of 56Fe/57Fe at the Earth.

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HIGH-ENERGY ASTROPHYSICS 1 987 371 1 988 15 -105 keV co cot oh o s Q U. so - X - - J 11 !1 1;1 111 ' 1 o , , ~1 1 ~I\_' 200 300 400 500 600 800 DAY AFTER TH E EXPLOSION FIGURE 2 The SN1987A X-ray 15-105 keV flux as a function of time according to the HEXE observations Each point corresponds to one observational day, the errors correspond to one standard donation. Three sigma upper limit on the flux observed in May-June 1989 is presented. the traces of a shock wave generated due to collision between the expanding envelope of the supernova and a stellar wind emitted by the presupernova on a red giant stage of the evolution. We were also unable to obsene traces of X-ray radiation of the stellar remnant - a young pulsar or an accreting object or any manifestations of emission connected with cosmic rays. MIXING OF RADIOACTIVE ELEMENTS IN TlIE EXPANDING ENVELOPE Early detection of the SN1987A hard X-ray radiation by the Ginga satellite and the Avant module (Dotani et al. 1987; Sunyaev et al. 1987a,b) was the first evidence of a radioactive 56Co strong mixing over the envelope volume (Itoh e! al. 1987; EbisuzaJ~ and Shibazaki 1988; Grebenev and Sunyaev 1988; Pinto and Woosley 1988~. At present this conclusion is confirmed by direct observations of a velocity dispersion of infrared lines of the iron and cobalt ions (Ericson et al. 1988) and also by a broad

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372 AMERICAN AND SOVIET PERSPECTIVES 1987 1 988 15 - 45 keV - o Q 10 0 - X O 4 o I I 1 1 1 /\ in 45 - 105 keV 1~ it, TO I I I ~ 105 - 200 keV L~1 1 \ \ 1 ~ T 200 300 400 500 600 800 DAY AFTER THE EXPLOSION FIGURE 3 The SN1987A X-ray fluxes as functions of time according to the HEM data in three colors 15-45, 45-105, and 105-200 keV. Each point presents data averaged over long period of observations The errors correspond to one standard deviation. The results of Monte-Carlo simulations carried out for the envelope model accepted in the present paper are shown by solid lines.

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HIGH-ENERGY ASTROPHYSICS 373 TABLE 1 The SN1987A X-ray flux evolution in accordance with data of the HEXE device observations in 1987-1989 Day since Fluxes and 1~ errors tI0~6phot~cm~2s~:keV~~] the outburst in :he energy bands 15 - 45 keV 45 - 105 keV 143.9 - 144.1 2. 34. 51. 12. 169. - 182. 68.2 5.7 46.7 2.1 186. - 204. 96.7 8.5 50.9 3.5 231. - 247. 83.1 8.3 57.4 3.3 258. - 266. 85. 10. 55.2 4.4 291. - 309 97. 11. 66.1 5.6 328. - 343. 100. 10. 62.6 3.5 413. - 426. 63. 9.5 51.1 3.8 444. - 446. 46. 27. 24. 12. 559. - 569. 17.2 9.6 20.5 4.1 590. - 599. 21.4 6.1 14.5 3.0 630. - 648. 12.2 4.1 10.6 2.6 820. - 840. 8.2 7.0 3.8 2.9 105 - 200 keV 18. 21.3 26.0 24.3 12.8 30.4 25.1 27.9 24.0 7.2 8.2 14.5 -2.8 17. 3.3 5.2 7.2 9.7 8.9 4.8 6.1 16. 6.5 4.7 7.0 4.2 spectral width of the 56Co direct escape gamma-lines (Matz e! al. 1988; Rester et al. 1989~. These direct observations testier to the presence of radioactive cobalt in the envelope layers having expansion velocities from 4~0 up to 3000 km/s. This would be impossible if the strongest mung of envelope material due to generation of the Rayleigh-~ylor instability had not occurred (Hachisu e! al. 1989; Arnett e! al. 1989~. The supernova hard X-ray light curve provides an opportunity to es- timate the distribution of radioactive cobalt over the envelope using the simplest assumptions. The 56Co distribution (mass-fraction) consistent with the observed light curve is shown in Figure 4 by crosses (the vertical line of a cross corresponds to an error at one standard deviation level). The problem of the reconstruction of cobalt distribution over the envelope is considerably simpler if cobalt radial distribution is searched as a superpo- sition of two Gaussians: a narrow one localized near the envelope center and an extensive one with broader 56Co distribution over the envelope. The regions of 56 Co distribution consistent with the observed light curve in this simple model are also presented in Figure 4. It is obvious that two different approaches give quite close results. About 60~o of cobalt is in the central region of the envelope having low

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374 o CD 11 o 10 10-1 o 10-2 C: a: G On On C 10-3 10-4 AMERICAN AND SOVIET PERSPECTIVES _ _~ o MASS, M 10 FIGURE 4 Region of the most probable s6 Co distribution (mass-fraction) over the SNl987A envelope which gates a possibility to simulate the observed X-ray light curves of the source. The results of two independent approaches are presented. In the first approach it is assumed that cobalt is uniformh~r distributed over five spherical layers of the envelope (crosses, errors of the cobalt concentration in each layer are given at one sigma level). In the second approach the 67% confidence level region of the distribution described by superposition of two Gaussians is obtained. It is clear that both approaches give similar results. velocities. And about 40% is mixed over all the envelope volume. Note that the data of only mro hard energy bands 45-200 keV were used dunog the cobalt distribution reconstruction. The flux at lower energies strongly depends on photoabsorption in the envelope, but the photoabsorption efficiency strongly depends on the degree of the cobalt nii~ng. All the calculations, the results of which were presented above and will be discussed below, were earned out on the basis of the velocit r

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HIGH-ENERGY ASTROPHYSICS 375 and density distribution model resulted from hydrodynamics simulations by Arnett (1988~. In Figure 3 it Is shown how the accepted model of cobalt distribution coincides with the observed X-ray light curve. Deviations are maximal at the beginning of the supernova X-ray observation in a soft 1545 keV band. This points out a more strong photoabsorption in comparison with photoabsorption ~ the used model. It may be connected with the enhanced cobalt concentration in outer envelope layers. High X-ray and gamma- ray radiation from these layers appeared at early stages of the envelope expansion before the beginning of the Roentgen observatory systematical observations. ABUNDANCE OF 57Co By the beginning of the second year after the explosion a 57Co isotope can become an important energy source in the supernova envelope since it decays 3.5 times more slowly than 56Co. The simulations of explosive nucleosynthesis (Woosley et al. 1986; Hashi~noto et al. 1989) predicted a ratio of 57Fe/56Fe abundances in the Earth. There are two ways to define the abundance of 57Co in the SN1987A envelope: the first, by direct determination of flux in the 57Co lines of 122 and 135 keV in the supernova spectrum and the second one, by the determination of a 57Co photon portion in the X-ray continuous spectrum in the 45-105 keV energy band. We mean the photons emitted in the 57Co lines 122 and 136 keV, but which undergo to multiple scattering in the envelope and decrease their energy due to the recoil effect. Because of relatively low energy resolution of Phosw~ch detectors, the HEXE device aboard the Mir-Kvant module gave considerably better results when the second method was used. The results presented below depend on an accepted envelope model (the Arnett model [1988] is used) and on a cobalt distn~ution over the envelope (the distribution presented in Figure 4 is used). It is also supposed that 57Co is distributed s~Darly to 56Co. For the whole period from September 1988 to June 1989 the Roentgen observatory has not detected a statistically significant enhancement of X-ray luminosity in the 45-105 keV energy band over the model predictions in which the whole observed flux is connected with the 56Co decay. The upper limits at three standard deviation levels for the ratio of 57 Co/56 Co relative abundance in the supernova envelope to the Earth's 57Fe/s6Fe relative abundance were equal to Z4 in September 1988, 3.3 in December 1988, and 1.8 in June 1989 at the accepted assumptions. Note that the ratio of 57Fe/56Fe abundances at the Earth is 0.024 (Cameron 1986~. All the data obtained from September 1988 to June 1989 allowed us to obtain a limit at three standard deviation levels for a portion of 57Co decay photons in the

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376 AMERICAN AND SOVIET PERSPECTIVES light curve of the SN1987A hard X-ray radiation. This limit corresponds to the 57Co/56Co abundance in 1.5 times exceeding the Earth's 57Fe/56Fe relative abundance. The observations in May-June 1989 gave the upper limit on the cobalt 122 keV line hm 3.9~10-4 photons cm~2s~: at 3 level). This limit corresponds in frames of the model being discussed to the 57Cop6Co abundance six times exceeding the Earth's abundance of s7Fe/~6Fe. The data obtained in May-June 1989 also provides a possibility to set up an upper limit on a fraction of the 22Na and 44Ti radioactive photons in the X-ray 45-105 keV flux from SN1987A in 830 days after the explosion. The corresponding upper limits at three standard deviation levels on mass of 22Na and 44Ti contained in the envelope at the moment of explosion are 1.3 10-3M~ and 9 10-3M~. These limits exceed the amount of 44Ti, M44 ~ 1.2 10-4M, and 22Na, M22 ~ 3 10-5M<3, predicted by Hashunoto e! al. (1989) and Woosley et al. (1986) on the basis of the explosive nucleosynthesis calculations at one order of magnitude. LIMITS ON THE STELLAR REMNANT LUMINOSITY The observations of the Roentgen observatory in May-June 1989 set up strong restrictions on X-ray luminosity of a stellar remnant produced during the explosion L~(1-6 keV) < 3.6 1036, Lo (6-15 keV) < 5.4 1036 and L=(15-105 keV) < 1.35 1037 erg/s for the assumed distance 55 kpc (Sunyaev et al. 1990, Able 1). At that time a Thomson optical depth of the envelope yet exceeded 3-4, and an X-ray spectrum of the remnant was considerably distorted by photoabsorption and compton scattering. The absorbed energy went on the envelope heating and was reemitted in the infrared, subnlillimeter, and optical bands. The measurements by Bouchet et al. (~1990) showed that emission of dust in the envelope had a black body spectrum with T ~ 160K, and the supernova bolometnc luminosity in 1030 days after the explosion was equal to (2.~0.1) 1038 erg/e. Using data from Monte Carlo calculations, the upper limit on the hard X-ray flux in the 15-105 keV band obtained by the HEXE device on the 83Oth day and the information on the envelope emission at low frequencies indicate that rather interesting restnchons on an intrinsic spectrum of the stellar remnant may be obtained. For example, assuming that the remnant (pulsars has a power law spectrum in 1-1000 keV energy band, Ion z'~= [photons cm~2s~ikeV~~], and using the 3cr upper limit presented above for the X-ray 15-105 keV flux escaping the envelope on the 830th day, we obtain the Or upper limit on the pulsar luminosity in the 1-1000 keV energy band JIB < 2.4 1~ and < 4.4 1~8 ergs for No spectral indexes ~ = 1.5 and 2.1. In neglecting the pulsar spindown and its luminosity changing we may find the upper limit on the energy absorbed in the envelope, that is,

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HIGH-ENERGY ASTROPHYSICS 377 its low frequency luminosity on the 1100th day LIR < 1.0 1038 and 3.5 1038 erg/s for c' + 1.5 and 2.1 correspondingly. It is clear that in the case when the spectral index is 1.5, such a spectrum is not able to give the observed low frequency luminosity of the envelope. It may be easily shown that any spectrum with cat < 1.75 does not coincide with the data obtained by Bouchet et al. (19901. The presented example shows a possibility for using our data to obtain restrictions on parameters of a pulsar hidden inside the expanding envelope. In the case when an accreting object is situated in the envelope center our estimates are less definite. Nevertheless, such an analysis, using the HEXE data presented above, for the object with a spectrum similar lo the spectrum of the well-known source Cygnus X-1 in a low state (Sunyaev and Thumper 1979), also demonstrates the impossibility of satisfying the low frequency data. If the infrared radiation is the result of dust, the reprocessing of a central object with hard emission from the X-ray spectrum of the stellar remnant should be soft enough Another way to explain the excess of infrared radiation detected by Bouchet et al. (19903 is that radioactive isotopes 57Co, 22Na and 44Ti are more abundant in the envelope than it was assumed. Their hard radioactive emission transforms in the opaque envelope into the low frequency emission which was observed. As the excess luminosity on the 1100th day after the explosion was equal to 2 1038 erg/s it was necessary that about 4 10-2M:, of 57CO (that is the 57Col56Co ratio exceeded the Earth's 57Fep6Fe ratio about 22 dines), or 9 10-4M~ of 22Na, or 9 10-3M of 44Ti were hidden inside the envelope. Comparing these values with the HEXE upper limits for 57Co, 22Na, and 44Ti abundances, M57 < 2.8 10-3M~ and M44 < 9 10-3M~, M22 < 1.3 10-3 Me, we come to the conclusion that the assumption about the radioactive nature of excess has failed in the case of 57Co and is unlikely ~ the case of 44Ti and 22Na. TTM/COMIS UPPER LIMITS ON THE FLUX FROM SN1987A The 11M/COMIS instrument on board the Kvant module is a coded mask-imaging spectrometer, sensitive in 2-30 keV energy, and with 7 .5 x 7.5 FWHM field of view. We present below some results of the anah,rsis of LMC field observations in November l9~June 1989. Dunng Ohs period about 130 sessions of LMC observations were per- formed. After the rejection of telemetric drop-outs and sessions with poorly defined pointing, the topical exposure time for the observations analyzed here was ~ 75,400 s. A slice of AM image (7.8 by 3.4) in three energy bands is presented on Figure 5. This unage was obtained by combining all the data of the period November 1988-June 1989. The sources LMC X-1, LMC X-2, LMC

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378 LMC X-1 LklC X-2 Ic ,N1987A _ . 80 LMC X-2 AMERICAN AND SOVIET PERSPECTIVES PSR 540-693 LMC X-4 LMC X-3 160-----a- -30 - ~i 1n frM/COMIS LMC 6-15 keV | SN1987A LMC X-4 _ PSR 540-693 ADO 40 80 140 - 1^ FIGURE 5 The 7.8 By 3.4 slices of LMC images in three dilierent energy bands (2-6, 6-15, and 15-Z7 keV) obtained By 1=I instrument during the observations of November 1988 - June 1989. The labels mark signifi~tl~r detected LMC sources as well as the position of SN1987A. Coordinates shown correspond to ITM field of view. One pixel of 1TM image has size of 1.86 arcmin.

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HIGH-ENERGY ASTROPHYSICS LMC X-2 LMC X-11 379 l1M/COMIS LMC 15-27 keV SN1 987A PSR 540-693 -40 LMC X-4 t60~ -30 -70 LMC X-3 10 X-3, LMC X4, and 50-millisecond pulsar PSRO54~693 are significantly detected. These sources are marked on Figure 5 by arrows as well as the position of SN1987N The AM observations of SN1987A in June-August l9g7 did not reveal any significant flux from the supernova in 2-30 keV energy band on the level 0.5 mCrab (3~) (Sunyaev e! al. 1987 a,b, 1988) when HEM and Pulsar X-1 devices onboard Kvant detected strong hard X-ray radiation from the supernova. The further TIM obsenations of SN1987A were stimulated by the exciting Ginga discovery of the variable continuum of this source in 130 keV band (Dotani ~ al. 1987; Masai et al. 1987; Masai et al. 1988~. During observations in November 1988 to June 1989 we again did not detect any significant flux from supernova in any part of 2-30 keV energy band (the efficiency of the TrM detector is highest at ~ 8 keV, and diminishes towards higher and lower energies). The upper limit in the whole 2-27 keV energy band is equal to 0.6 mCrab for Crab-like spectrum. The upper limits obtained in three energy subbands are presented in Able 2. In each particular session of observations (~ 1000 sec duration) we obtained an upper limit for the flux in the 2-27 keV band on the level of 5 mCrab. For each week's set of intense observations in November, December, or June, our 3a upper limit in the 2-27 keV band is on the level of 1.2 mCrab. This upper limit is twice lower than the January 1988

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380 AMERICAN AND SOVIET PERSPECTIVES TABLE 2 Upper limits (3 cr) of the flux from SN1987A obtained by TI M instrument dunog the observations in November, 1988 - June, 1989 Energy (key) mCrabtl ~ ph/3ec/cm2/kev ~ 2 ergs/e 2 - 6 0.S 4~10~ 4 ~ . O ~ )0- ~ ~ 6 - 15 0.9 lal0~4 1.5~10-~t 15 - 27 4.2 ~ ~o~4 4.0 30-~} ) for Crab-like spectrum 2 ) for flat photons spectrum outburst detected by Ginga in the same spectral band (Masai et al. 1988~. Unfortunately, the AM instrument did not operate when the source in the standard X-ray band, detected by Ginga, was the most bright. The data presented here corresponds to the time when the brightness of this source in hard X-rays decreased. Therefore we can only mention here that during periods of our observations, the standard X-ray band source in SN was in a relatively quiescent state with no outbursts of the January 1988 type. All the HEXE upper limits for the September 1988 to June 1989 time span are below the TIM 3~ upper limits for the 16-17 keV band for any power law extrapolation of detected HEXE nux towards lower energies with photon spectral index ~ > - 4.5. The change in shape of the SN1987A spectrum, according to the HEXE data, in September 1988 undoubtedly shows that any flux at energies lower than 40 keV has an origin unrelated to the radioactive decay of both 56Co and 57Co. This fact makes a search for the flux from SN1987A ~ the standard X-ray band of eno:rn~ous importance because it opens the way to discover X-ray emissions of a different, unknown nature, and therefore is more attractive for further investigation. CONCLUSION All the data obtained by the four HERE detectors in August 1987 to January 1988 confirm the identification of the hard X-ray source in the Large Magellanic Cloud having an unusual spectrum (see Figure 6) with SN1987N The upper limits at 3 OCR for page 368
~ 1.0 0.8 0.6 ~ 0.4 o o 0.0 -0.2 -0.4 -06 ~1 @ @ / t % \ lx ~ @ _ ~ /// ~ ~ it/ ~ In// ~ ~ a' @ / / 06 0.4 0.2 0.0 -0.2 -0.4 -0.6 DEGREES nG~ 6 anion of lbe ban <~ =~ ~ me Awe ~ag~lanic cloud awning Ill. ~e=~_~, and ~ ~ slant for 1be enemy bong 13~ (dolled ~- and ~-1~ ~ and hem ~ pant. P=ilio~ of The ~ ARC <1 (1), PER 03~3 ha, SN1 ~d. IS of me ~ d-= ~ ~1 ads of o-~1io~ am sb~ sell

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382 AMERICAW AND SOVIET PERSPECTIVES TABLE 3 The upper limits on the X-ray flues (in photons cm -2 S-1 keV~~) from LMC X-1 and PSR 054~693 at three standard deviation level ~ accordance with the HEXE data obtained in 1987 August - 1988 January. They were reconstructed during localization used a number of offset observations source | ls-45 keV | 4s- 105 keV LMC X-1 5.s 10-s ~ 0 10-6 PSR 0540-693 2.9 ~ 10 s 6. 8 10- 6 confident signal from the SN1987A region in spite of other X-ray sources LMC X-1 and PSR 0540~93 having been in the HEXE field of view. Ikking into account the donations between the direction of the telescope axis and directions on these X-ray sources, an efficiency of the flux detecting from different sources differed. The upper limits on the flues from SN1987A and other sources are presented in Figure 1 and 7 and also in 1kble 4. The weakness of the hard X-ray flux from LMC X-1 in May-June 1989 (Sunyaev et al. 1989) and the closeness of the upper limit on the LMC X-1 hard emission obtained by the HEXE device to limits obtained during the HEAO A2 (Wait and Marshall 19843 and HEAO A4 (Matteson and Peterson 1987) experiments, testis to a small portion of the LMC X-1 flux to the flux detected by the Kvant module during August 1987 to April 1988. Note Hat the 0= detected in January 1988 exceeds the upper limits obtained in May-June 1989 are about one order of magnitude. Note in conclusion that the supernova light curie in 45-105 keV energy band did not show a single sharp statistically confident burst similar to the burst observed by the Ginga satellite in January 1988 in the softer energy band. In hard X-rays the light curie was smooth as it was expected for the light curve of the source connected with radioactive decay. ACKNOWLEDGEMENTS The authors are grateful to V.D. Blagov, V.M. Loznikov, VG. Rodin, AM. Prudkog~d, the team headed by YmP. Semenov, and the cosmonauts working aboard the Mir space station for the observatory control.

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HIGH-ENERGY ASTROPHYSICS 10-1 1o2 1 LMC X-1 1 1 11 11 - . . >E 10 3 ,.\ I TO ~g 1 0 ~\ JO 6 ~1 1 0.5 1.0 5.0 10 _ 1 100 ENERGY (keV) 104 PSR 0540-693 C) _ _ .O N C 105 _ o _ o _ _ - X _ lL _ 10-6 3283 \ \ , , , , , ,,,, \ , 10' 1o2 ENERGY (keV) FIGURE 7 (a) Spectrum of LMC X-1 according to the HEAO A2 experiment (crossest (Wait et al. 19843. The upper limits on the hard X-ray flux from this source according to the ElEXE data. Ibe analytical approximation of the 11M instrument data is shown By a solid line (Sunyaev et al. 1990~. (by Spectrum of PSR 0540~93 (a power law approximation) in accordance with the observatory Einstein (Claris et al. 1982; Seward et al. 1984) and the upper limits on the hard X-ray 0= according to the HEXE data. The spectrum obtained by the 11M instrument (Sunyaev et al. 1990) coincides with the presented power law approximation within the limits of experimental data errors.

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384 AMERICAN AND SOVIET PERSPECTIVES TABLE 4 The average efficiencies of the observatory Roentgen pointing and the corresponding upper lets at three standard deviation levels on the X-ray fluxes (in photons cm -2 s-1 keV~l) from the LMC sources observed by the HEM device in 1989 May-June. Source Ef f iciency 15- 45 keV45- 105 keV . ; SNl987A 52 % 2. 1-10 s 8 6 10-6 LMC X-1 1 32 % 8.5-10-s ~ 1.2 10-5 PSR 0540-693 45 ~3 .4 10 ~ s 9, 5 . 10~ 6 REFERENCES Arnett, W.D. 1988. Astrophys. 3. 331:377. Arnett, W.D, B.A. Fryxell, and E. Muller. 1989. Astrophys. J. Lettem 341:L63. Bouchet, P., IJ. Danziger, and LB. Lupy. 1990. IAU Circa No. 4933. Cameron, AJ.W. 1986. Page 33. In: Barnes, C4, D.D. Clayton, and D.N Schramm (eds.~. Nuclear Astrophysics. Moscow: Mir. Clark D.H., I.R lbohy, KS. Long, et al. 1982. Astrophys. J. 255:440. Dotani, I, K Hayashida, H. Inoue, et al. 1987. Nature 330:~0. Ebisuzaki, 1:, and N. Shibazaki. 1988. Astrophys. J. Letters 3Z7:L5. Englhauser, J., S. Doebereiner, E. Pietsch, et al. 1989. 23d ESLAB Symp. Pro~ Enckson, E F., M.R Haas, S.WJ. Colgan, et aZ. 1988. Astrophys. J. Letters 330139. Grebenev, SN, and RA Sunyaev. 1988. Soviet Astron. Letters 14:675. Hachisu, I., ~ Matsuda, K Nomoto, and 1: Shigeyama. 1990. Astrophys. J. Letters. In press. Hashimoto, M., K Nomoto, and 1: Shigeyama. 1989. Astron. Astrophys. 20:L5. Itoh, M., S. K~ gai, 1: Shigeyama, et a~. 1987. Nature 330:233. Masai, K, S. Hayakawa, H. Itoh, et al. 1987. Nature 330 235. Masai, K, S. Hayakawa, H. Inoue, et al. 1988. Nature 335:8~04. Matteson, J.L, and L.E. Peterson. 1987. Pnvate communication. Matz, S.M., G.H. Share, M.D. Leising, et al. 1988. Nature 331:416. Pinto, Pa., and S.E. Woosley. 1988. Astrophys. J. 329.820. Rester, AS., RL Coldwell, F.E. Dunnam, et al. 1989. Astrophys. J. Letters 342 L71. Seward, F.D., F.R Harnden, and DJ. Helfand. 1984. Astrophy~ J. Letters 287:Ll9. Sunyaev, R^, AS. Kaniovsky, V.V. Efremov, et al. 1987a. Nature 330:227. Sunyaev, R^, ~S. Kaniovsky, V.V. Efremov, et al. 1987b. Soviet Astron. Lettem 13:1027. Sunyaev, RN, V.V. Efremov, AS. Kaniovks~r, et al. 1988. Soviet Astron. Lettets 14:579. Sunyaev, R^, AS. Kaniovsky, V.V. Efremov, et al. 1989. Soviet Astron. Letters 15:291. Sunyaev, R^, M.R Gilfanov, E.M. Churazov, et al. 1990. Soviet Astron. Lette~s. In press. Sunyaev, R4, and J. Ih~emper. 1979. Nature 279 506. White, N.E., and F.E. Marshall. 1984. Astrophys. J. 231:354. Woosley, S.E., and TA Weaver. 1986. Page 359. In: Barnes, C4, D.D. Clayton, and D.N. Schramm (eds.~. Nuclear Astrophysics. Mosoow: Mir.